I. Field of the Invention
This invention relates generally to a system for copying and duplicating flexible magnetic storage diskettes, and more specifically, a system which permits the copying and duplication of such magnetic storage diskettes on a high-volume basis irrespective of the mode in which the magnetic information is recorded and the format employed for organizing the digital information on the diskette.
II. Discussion of the Prior Art
In recent years there has been an explosive growth in the number of personal computers and minicomputer systems installed throughout the world, and this growth is expected to compound dramatically through the rest of this decade. These computer systems are typically 8 or 16-bit microprocessors and 32 bit minicomputers, both of which rely extensively on flexible magnetic disk or "floppies" for their program and data input.
Whereas, in the past, the number of copies of a program which had to be prepared was relatively low while the selling price of the program was high, often in the thousands of dollars, it intended to make the cost of duplication of the program a relatively insignificant issue. Personal computer software typically sells in the $50-$200 price range and literally thousands, and perhaps in the future millions, of copies of a particular program will be produced. What is required for low-cost mass duplication of information on floppy diskettes is the equivalent of the modern day printing press. However, whereas the printing press can be modified to print virtually any material for any use by merely changing the printing plates, it is not that simple in the duplication of magnetic storage diskettes. Virtually every computer system employs a different diskette standard, where these differences will cover the physical size of the diskette, i.e., 3 in., 31/4 in., 31/2 in., 51/4 in. or 8 in. diameter, the manner in which the digital information is encoded into the magnetic domains, i.e., FM, MFM, M.sup.2 FM, GCR and, even more diversely, the format or structure which is used to organize the data on the diskette.
Each computer system has developed a unique combination of dedicated high-speed hardware and software to perform the read and write operations for a particular diskette standard. It cannot accommodate any other standard typically. We thus have a real "Tower of Babel" syndrome in the computer industry. Duplication of programs is even further complicated by the use of copy protection schemes of software publishers which make it very difficult, if not impossible, for a user of the software to make his own copies with his equipment. Software publishing to date has been virtually a Guttenberg-type process, with the duplication of diskettes being done on very special purpose hardware with very low production rates.
The present invention enables very low-cost, high-speed duplication of diskettes, e.g., 4,200 per hour in a maximum configuration, for the diskette size mentioned for any of the encoding standards in use and it will accommodate any variety of formats presently used or which may be derived in the future, including formats which are copy-protected. Whereas, conventional techniques can potentially achieve this level of versatility at very low production rates or, conversely, low versatility at high-production rates, the novelty of the present invention resides in special purpose apparatus which will accomplish both ends. That is to say, through a combination of special purpose high-speed logic, which makes extensive use of large scale integrated circuits and programmable array logic "PALs", coupled with a unique architecture which allows the duplication process to be done in parallel on a plurality of slaves, e.g., 30 or even more, both high volume and high versatility are achieved.
A conventional 16-bit microprocessor, executing a program out of eraseable programmable read-only memory (EPROM), provides supervisory control for the dedicated high-speed logic.
In that in all digital magnetic recording, regardless of the media, the method of encoding the data or the data format, involves the periodic reversal of magnetized states on the magnetic media, i.e., flux transitions, this is the common denominator of all recording systems. The entire duplication process of this invention deals with information represented in the form of the time of occurrence of flux transitions. This is the most detailed representation of the data and thus requires higher speed logic circuitry to deal with it, but it is the most general form of the data and this is the feature that enables complete versatility of duplication. Reliable high-speed duplication requires three revolutions of the object diskette for each track of information, one revolution to acquire the track, a second to write the data onto the track and the third to verify the integrity of the track by comparing the information read to what was intended.
A major issue in digital magnetic recording is the need for good data interchange margins such that information recorded on one system can be reliably read on another. The software publishing business is unique in its requirement that the programs be distributed to a very wide number of user systems, often with a considerable delay between the time the information is written and the time it is first attempted to be read by the user. These factors place an exceptional emphasis on data interchange margins, and an object of this invention is to assure the tightest possible tolerances on recording amplitude and timing to provide the widest possible data interchange margins.